In recent years, various techniques have been developed to increase the recording capacity of magnetic disk devices. Among these techniques is a recording technique called “shingled-recording method.” The shingled-recording method is a recording method in which information is recorded on a track that is an unit of recording in such a manner that overwriting is performed on part of an adjacent track (partial overwriting). In the shingled-recording method, a track group including plural adjacent tracks is defined as a unit of recording.
In the shingled-recording method, when information is to be newly recorded on a midway track of the tracks of a track group, it is impossible to subject only the midway track to rewriting. In this case, it is necessary that at least the tracks following the midway track be subjected to the rewriting. A technique for detecting an erroneous recording phenomenon called “drifted-off writing” to determine necessity of rewriting is known. The drifted-off writing is a phenomenon that information is recorded erroneously on a track that is adjacent to a true recording track due to a shift (drift) of the recording head during the recording. In this technique, whether rewriting is necessary or not is managed on a track-by-track basis and information is rewritten to a location where a determination “rewriting is necessary” was made. For example, information rewriting is performed on a recording track or a track adjacent to it.
However, in the shingled-recording method, information rewriting on a recording track and an adjacent track that is adjacent to the recording track and on which the recording track is overlapped cannot be performed efficiently or properly.